WTC2005-63696 FRICTION AND WEAR BEHAVIOR OF BORONIZED CHROMIUM FOR BIOLOGICAL APPLICATIONS

ABSTRACT Enhanced corrosion and wear resistance are crucially important to prolong the service life of biomaterials. Boronizing has been reported to enhance the wear resistance of pure chromium. In this research, we investigate friction and wear behavior of boronized chromium. Pin-on-disc tribometer was used to conduct the wear and friction tests. Experiments were conducted in dry conditions as well as in simulated body fluid (SBF). Fundamental aspects of wear mode and lubrication behavior were studied using surface characterization techniques such as TEM, and X-ray diffraction. Results showed evidence of tribo-chemical interactions between SBF and work piece materials. INTRODUCTION Boride coatings have been applied to metal surfaces in order to improve their corrosion resistance, electrochemical properties, tribological performance, and to prolong service life [1, 2, 3 and 4]. Boronizing is one way to form this uniform coating on the substrate material. It is a thermo-chemical diffusion surface treatment in which boron atoms diffuse into the surface of the work piece to form hard borides with the base material

WTC2005-63696 FRICTION AND WEAR BEHAVIOR OF BORONIZED CHROMIUM FOR BIOLOGICAL APPLICATIONS

ABSTRACT Enhanced corrosion and wear resistance are crucially important to prolong the service life of biomaterials. Boronizing has been reported to enhance the wear resistance of pure chromium. In this research, we investigate friction and wear behavior of boronized chromium. Pin-on-disc tribometer was used to conduct the wear and friction tests. Experiments were conducted in dry conditions as well as in simulated body fluid (SBF). Fundamental aspects of wear mode and lubrication behavior were studied using surface characterization techniques such as TEM, and X-ray diffraction. Results showed evidence of tribo-chemical interactions between SBF and work piece materials. INTRODUCTION Boride coatings have been applied to metal surfaces in order to improve their corrosion resistance, electrochemical properties, tribological performance, and to prolong service life [1, 2, 3 and 4]. Boronizing is one way to form this uniform coating on the substrate material. It is a thermo-chemical diffusion surface treatment in which boron atoms diffuse into the surface of the work piece to form hard borides with the base material

Characterization of gas tunnel type plasma sprayed hydroxyapatite-nanostructure titania composite coatings

Hydroxyapatite (HA) can be coated onto metal implants as a ceramic biocompatible coating to bridge the growth between implants and human tissue. Meanwhile many efforts have been made to improve the mechanical properties of the HA coatings without affecting its bioactivity. In the present study, nanostructure titania (TiO2) was mixed with HA powder and HA–nanostructure TiO2 composite coatings were produced by gas tunnel type plasma spraying torch under optimized spraying conditions. For this purpose, composition of 10 wt% TiO2 + 90 wt% HA, 20 wt% TiO2 + 80 wt% HA and 30 wt% TiO2 + 70 wt% HA were selected as the feedstock materials. The phase, microstructure and mechanical properties of the coatings were characterized. The obtained results validated that the increase in weight percentage of nanostructure TiO2 in HA coating significantly increased the microhardness, adhesive strength and wear resistance of the coatings. Analysis of the in vitro bioactivity and cytocompatibility of the coatings were done using conventional simulated body fluid (c-SBF) solution and cultured green fluorescent protein (GFP) labeled marrow stromal cells (MSCs) respectively. The bioactivity results revealed that the composite coating has bio-active surface with good cytocompatibility

Characterization of UHWPE-TiO2 Composites Produced by Gelation/Crystallization Method

In this study, ultra-high molecular weight polyethylene (UHMWPE) - TiO2 composites reinforced with TiO2 particles with weight ratios of 0.5, 1 and 2% were produced by gelation/crystallization method in decalin+antioxidant solution of UHMWPE at 150 degrees C, for 40 min by using magnetic stirrer. The gel mixture was cooled in an aluminum tray embedded in iced water under ambient conditions and dried in an oven at 130 degrees C for 90 min to remove any residual trace of decalin. Distribution and elemental analyses of TiO2 particles in polymer matrix was examined by SEM-EDS. Crystallization behavior was investigated by differential scanning calorimetry (DSC). Based on the results, TiO2 particles in the UHMWPE have accelerated the crystallization, acting as nucleating agents, with increment from 56% for UHMWPE to 63.5% for UHMWPE-2 wt% TiO2. The present bond types in composites were analyzed by Raman spectroscopy and the results are in good agreement with literature. Uniaxial tensile tests were performed to determine Young's modulus of UHMWPE-TiO2 composites. It was found that Young's modulus of UHMWPE was increased from 52 MPa to 800 MPa with the addition of TiO2 particles

Morphological Differences and Their Effects on the Mechanical Properties of Titanium Oxides Thin Film Obtained via Anodization Process

It is well known that anodization process is helpful for obtaining metallic oxides on the metal surfaces. The advantages of this process are used in this study to obtain rough surfaces consisting of titanium oxides and solid solutions of titanium and oxygen. Two different voltages were applied to a pure titanium foil during two process time periods. In all process conditions, titanium oxide thin films were successfully obtained on the base material. Depending on the duration of the process and the voltages applied, the amount and the sizes of oxide particles were changed. EDX analysis combined with SEM and AFM clearly showed that rough surfaces were obtained. Having rough surfaces would be helpful for bonding to another material. However, in the micro-nano scale it is clear that the inhomogeneous mechanical and chemical properties were obtained, most probably resulting in inhomogeneous crack initiation

Effect of particle size on microstructural and mechanical properties of UHMWPE-TiO2 composites produced by gelation and crystallization method

In this study, Ultra-high-molecular-weight polyethylene (UHMWPE) in 0.5 wt % concentration-0.5, 1, and 2 wt % nanosized and micron-sized TiO2 composites were produced via gelation/crystallization method in decalin + antioxidant solution at 150 degrees C for 45 min by using magnetic stirrer. The gel composites were cooled in an aluminum tray embedded in iced water under ambient conditions and dried in an oven at 130 degrees C for 90 min to remove any residual trace of decalin and to strengthen the UHWMPE matrix. Scanning electron microscopy-EDS images indicate that TiO2 particles were integrated well with the polymer matrix. differential scanning calorimetry studies revealed that the crystallinity of pure UHMWPE was calculated as 56% and an increase of 13.32% for micron sized and 19.25% for nano sized TiO2. Crystalline and amorphous phases of UHMWPE-TiO2 composites confirmed by Raman are in good agreement with the literature. The elastic modulus of test materials ranged from 610 to 791 MPa for micron sized and raised from 675 to 1085 for nano sized reinforcing agents. Ultimate tensile stress increased about 35% for micron sized and 60% for nano sized weight 1% TiO2 reinforced composites. Biomineralization tests (performed in stimulated body fluid, at 37 degrees C and 6.5 pH during 1 month) have shown that produced composites are compatible as acetabular liner replacement for hipjoints due to no accumulation (Ca, P, Na, etc.) on UHMWPE-TiO2 composites. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47402

The importance of Lp(a)-fibronectin interaction in atherogenesis

An elevated concentration of lipoprotein (a) (Lp(a)) in serum has been considered a risk factor for coronary heart disease by various investigators. The apo(a) portion of Lp(a) binds to the carboxyterminal heparin binding domain of fibronectin. Lp(a) bound to fibronectin is internalized through the fibronectin receptor pathway and thereby causes increased accumulation of lipid and foam cell formation. In the present study, fibronectin and Lp(a) concentrations have been assayed in patients with coronary heart disease (CHD) and healthy subjects